The ASCAT on MetOp series of scatterometers promises to be a long-term source for ocean vector wind data and a complement to QuikSCAT and future US scatterometer missions, as recommended by the NRC Decadal Review. We have now had close to one year of joint operation of QuikSCAT and ASCAT, and the joint data set presents a unique possibility to assess the relative performance of the two instruments. This talk presents the work conducted at JPL to cross-validate and compare the two instruments. In the first part, we present our assessment of the measurement resolution and error characteristics of both instruments. As a first step, we use traditional validation methods, such as comparing against independent ground truth and models, and data comparisons of space-time coincident QuikSCAT/ASCAT data. We complement these studies by examining the spectral resolution characteristics of each instrument. This technique allows us to estimate the instrument resolution and noise characteristics. In the second part, we examine the geographical distribution of climatological mean differences between the two instruments (after correcting for diurnal variability). We find different responses for winds estimated using Ku and C-bands. Some of these differences are associated with Sea Surface Temperature fronts, while others have basin scale signatures. We examine potential sources of these differences, including instrumental biases, rain contamination, model function biases, estimation biases, and different surface responses to wind and wind stress at Ku and C-band.